Refining of animal and vegetable oils



Patented Dec. 4, 1951 OFFICE REFINING OF ANIg/iilg AND VEGETABLE Morris-Mattikow, :New York, N. Y.

NdDrawing. Application December 4, 1946, Serial N 0. 713,927

12 Claims.

This invention relates to the refining of animal and' vegetable oils, and'more'particularly, to the refining of such oils at low temperatures and while they contain an organic solventfor the oils.

In my copending application, Serial No.700,830,

filed October 2, 1946, of which the-present application is acontinuation-in-part, I have disclosed a process of refining animal and vegetable oils in which the oils are either-partially or completely refined in the presence of a limited amount of organic solvent for the oil. Such a process is particularly useful in the refining of solvent extracted cottonseed oil in order to reduce the color of the oil but is advantageous in the refining of glyceride oils in general. Below certain critical maximum ratios of solvent to oil, removal of impurities such as gums and free fatty acids'from the oil is readily accomplished. In alkali refining operations, the color of highly colored oils, such as solvent extracted cottonseed oil, is also markedly reduced. If themaximum critical ratio is exceeded, the resulting oil is high in color as the solvent holds a portion of the coloring matter in solution in the oil phase. It has not proved practical to attemptito removethis coloring matter by subsequent bleaching .operations.

Solvent extraction of .cottonseed oil has been suggested and such solvent extraction does remove a greater amount of oil from the seedthan the conventional processes employing hydraulic presses or expellers. Solvent extraction of cottonseed oil has not, however, been extensively employed commercially. Difficulty has been-encountered in producing a commercially acceptable refined oil from the solvent extracted cottonseed oil. The major difficulty has been the inability to produce a refined oil of sufiiciently low color to meet the standardsof the cottonseed oil industry. In other words, solvent extracted cottonseed oil contains much more coloring matter than pressed or expelled oil and it has not been heretofore possible to-economically remove the excess coloring matter from the oil. Suggested processes involving substantially complete removal of the solvent from the solvent extracted oil prior to refining have not proved practical since such processes have either required subjecting the oil to elevated temperatures for a sufficient length of time to set the color in the oil or have required expensive and time-consuming solvent stripping operations with steam at low temperatures and under high vacuum. The latter type of operation ordinarily resultsin difficultly resolvable water-in-oil "emulsions requiring :additional emulsion breaking steps.

These difliculties are overcome when the oil is refined in the presence of'a limited amount of solvent since no difficulty is encountered in reducing the amount of solvent to below the maximum critical ratio referred to above.

A greater ratio of solvent to oil than the maximum critical ratio also causes an increase in the phosphorous content'of the refined'oil showing that the gums, including the phosphatides, have not been adequately removed inthe alkali-refining operation. This is not peculiar to cottonseed oil but occurs in substantially all glyceride oils. .Asimilar action occurs with respect to partial refining or degumming of glyceride oils as well as in acid refining in the presence of an oil solvent,:for example in producing a non-break oil. If the ratio of solvent to oil in a degumming operation exceeds a maximumratio the solvent holds .a portion of the gums in solution in the oil solvent mixture, thus reducing-the recovery or" the valuable gums as a by-product and producing an inferior degummed oil. The same thing occurs in acid refining thus resulting in failure to produce a non-break oil. After the gumsv have been removed in any type of degummine or refining operation, the remaining solvent can be removed from the oil without difficulty.

Ithas now been found that operating either a degumming or a refining process at a lower temperature than those contemplated in my prior application provides for more effective separation of undesired impurities. A further reduction of colorlin the alkali refining of highly colored oils, such as solvent extracted cottonseed oil, enables certain of these oils which could not be brought to an acceptable low color by even the process of my said copending application, to be refined to a color well below the maximum set by the industry. Ineither alkalirefining or degumming operations, the gums are'more cleanly separated from the oil as shown by the fact that the phosphorous content of the oil is further reduced. The presence of the solvent enables such lower temperatures tobe employed since itmarkedly reduces'theviscosity ofthe oil in the refining mixture. In the case of solvent extracted oil the lower temperatures contemplated in the present invention can be easily secured by evaporation of excess solvent. A greater, yield of oil is obtained and a better qualityoiliis-produced from any crude glyceride oil by any :of the refining steps contemplated in the present invention.

The .lower temperature operation also has utility in the acid refining of glyceride oils. Such acid refining is employed primarily in the treatment of drying oils for paints and the like and is distinguished from degumming or alkali refining operations by the employment of a strong mineral acid, usually concentrated sulfuric acid, to coagulate the mucilaginous material in the oil and render it separable. The lowered temperatures minimize the attack on the glycerides, such as charring or sulfation, by the strong acid and the lowering of the viscosity of the oil by the presence of the solvent enables the lower temperatures to be employed. Again adequate separation of precipitated impurities can be accomplished only if the amount of solvent is below a critical upper limit.

It is also many times desirable to remove the more saturated components from refined oils, for example, to increase the stability of salad oils against precipitation of saturated glycerides in cold weather and to increase the drying properties of oils employed in paints. The refined oil from the process of the present invention is at a low temperature when separated from its precipitated impurities and will usually still contain a substantial amount of solvent. Evaporation of at least a portion of this solvent may be employed to further reduce the temperature of the oil. By holding a chilled alkali refined oil at a low temperature the stearine or other saturated components thereof crystallize out of solution after which the crystallized material may be filtered or otherwise separated from the oil and solvent mixture. By carrying the temperature of the oil to still lower temperatures, it is many times possible to fractionate a refined oil and solvent mixture into two or more fractions, one containing the solvent and the portion of the oil higher in unsaturated glycerides and the other containing the portion of the oil higher in saturated glycerides.

It is therefore an object of the present invention to provide an improved process for refining oils at low temperatures and in the presence of a solvent for the oil in an amount below a critical upper limit.

Another object of the invention is to provide an improved process of refining solvent extracted cottonseed oil in the presence of a portion of the solvent and at low temperatures in order to produce a refined oil of low color.

Another object of the invention is to provide an improved process of refining solvent extracted oils at low temperatures and in the presence of a portion of the solvent in which the evaporation of the solvent is employed to produce such low temperatures.

Another object of the invention is to provide an improved process of partially refining or alkali-refining glyceride oils in which the oil is treated with a refining reagent and separation of impurities is accomplished at low temperatures and in the presence of a limited amount of solvent for the oil.

A further object of the invention is to provide an improved process of acid refining of glyceride oils in the presence of a small amount of solvent and at low temperatures to minimize charring and other attack on the oil.

A still further object of the invention is to utilize the lower temperature of the oil separated from precipitated impurities by the present invention to assist in removing the more saturated glycerides from the oil.

In common with the process of my copending application, supra, the apparatus employed in carrying out the refining procedures of the pres- 4 ent invention may be that of the Thurman Patent No. 2,260,731. This patent may be referred to for a detailed description of such apparatus and process steps as are not described in detail in the present application.

A solvent extracted oil will ordinarily contain at least as much solvent as oil by weight. That is to say, the ratio of solvent to oil will ordinarily range from 1 to 1 to 10 to 1. For refining operations in accordance with the present invention, this ratio of solvent to oil must be reduced below a critical maximum ratio. For degumming and acid refining operations, this maximum ratio is approximately 1 to 4., i. e., the oil should contain not greater than approximately 25% solvent based on the weight of the oil. For alkali-refining operations, the maximum ratio is approximately 1 to 3, i. e., the oil should not contain greater than approximately 33% solvent. The critical maximum ratios of oil to solvent will vary somewhat with different oils and difierent solvents therefor and may also increase slightly as the temperature of the process is decreased, but for any given oil and solvent mixture and temperature of treatment, effective refining treatment cannot be accomplished if the ratio of solvent to oil exceeds critical maximum values which are always close to those stated above.

The excess solvent can be removed from solvent extracted oil by any suitable low temperature distillation process, for example, the fiash distillation step of the Thurman patent, supra. By employment of a relatively high vacuum, the oil from the distillation step may be brought to a desired temperature for the refining operation. In any of the refining operations contemplated by the present invention in which a liquid refining agent is added to precipitate impurities this temperature will ordinarily be between 30 and 60 F., and preferably in the range of approximately 40 and 50 F. It will be apparent that the temperature obtained will depend upon the initial temperature of the oil solvent mixture and the amount and nature of the solvent removed from the oil. The amount or" solvent removed will in turn depend upon the vacuum employed in the distillation step, the temperature of the oil-solvent mixture entering the distillation step as well as the nature of the solvent and the time of vacuum treatment. All of these factors may be correlated to produce the required final temperature and solvent content of the oil. Thus, the oil entering the distillation step may be either heated or cooled and the degree of vacuum and the time of vacuum treatment adjusted to the required value. By adjusting the various factors referred to, an oil containing the required amount of solvent and at the required temperature can be easily obtained. it will ordinarily not be necessary to heat the oil entering the distillation step and it is desirable to avoid high temperatures at any time during the process. If necessary, the oil can be heated as high as F. without danger of setting the color in highly colored oils and temperatures as high as 220 F. may be employed if the oil is not maintained at this temperature for an extended period of time, for example, not in excess of 15 minutes. The setting of the color in the oil is a function of both time and temperature and the higher the temperature, the shorter the period of time at which the oil can be maintained at the higher temperature.

By reducing the solvent to below approximately 25% of the oil, the gums including the phosphatides can be substantially completely removed from the oil by a degummings'tep at the low temperatures discussed above. In such a step an aqueous precipitating agent is thoroughly admixed with the oil and solvent mixture. The precipitating agent may be water "alone or'a solution of substantially any electrolyte, either acidic, neutral or basic. If substantially "neutral salts or other electrolytes which do not attack the oil or the gums, such as weak acids or bases, are employed the solution may be relatively concentrated while for strong acids or bases, a very dilute solution may be used. The precipitating agent may also contain water-miscible organic solvents such as alcohols which are substan- *tially immiscible with the oil and extraction solvent at the temperature of the degumming operation. The amount of aqueous precipitating agent will usually range between 1% and 10% on the basis of oil solvent mixture, the best results being ordinarily obtained with from 5% to 6% precipitating agent. The resulting fo'ots, including the precipitated gums, can be separated from the oil solvent mixture in any desired manner, such as settling or decantation, although continuous centrifugal separation produces the best results and is preferably preceded by a continuous mixing step for admixing the agent with the oil.

The temperature during the mixing of the oil with the degumming reagent and during separation of the precipitated. gums from the oil will vary with the oil being treated. This temperature will ordinarily range between30 F. and 60 F., and for most oils, a temperature between 40 and 50 F. gives the best results. Ordinarily, the temperature of mixing and separation will be substantially the same butin some cases the best temperature for separation may be somewhat higher or somewhat lower than the mixing temperature and in such cases it'is possible to either cool or heat the oil slightly between mixing and separation. In the presence of a small amount of solvent, the gums readily separate from the oil at the low temperatures employed. A considerable amount of coloring matter separates with the gums in the treatment of highly colored oil, such as solvent extracted cottonseed. oil. At the low temperatures and in the presence of the solvent, most of the unsaponifiables, however, usually remain in the oil and this is advantageous as such unsaponifiables contain naturally occurring anti-oxidants thus producing a more stable oil.

An alkali-refining operation, either after a preliminary degumming operation such as just de scribed, or upon a crude oil solvent mixture requires that the solvent content be below approximately 33% of the oil. Oil from a prior degumming operation will contain in the neighborhood of 25% solvent or 'lessand such oils can ordinarily be satisfactorily alkali-refined in accordance with the present invention. In the case of a crude oil which has not be degummed, it is unnecessary to reduce the solvent below the 33% referred to. An alkali-refining operation involves the admixture of an aqueous solution of an alkali with the oil to cause the alkali to react with the free fatty acids in the oil to form soapstock which may be separated from the oil solvent mixture in any suitable manner such as settling, decantation or filtering, although the preferred separation is bycontinuous centrifugal separation. Thus, the mixing of the alkali solution with the oil solvent mixture may be carried on continuously as described in the Thurman patent, supra, and the separation also accom plished by continuous centrifugal "separation, as also described in the Thurman patent.

In general, a caustic alkali, such as caustic soda or caustic potash, is necessary for color removal in the alkali refining step. The amounts and concentrations of alkali solutions vary with the nature of the oil and the correctamounts and concentrations are known to the prior art. That is to say, the refiner determines the free fatty acid content of the oil, calculates the equivalent amount of alkali, and adds the alkali in the form of an aqueous solution of the proper concentration as determined byexperience and publications known to the art and in :an amount providing a predetermined excess over that required toneutralize the free fatty acids. Best results are usually secured with concentrations in the neighborhood of 20 B. although the concentration may vary between approximately 12 to 30 B. The mixing and separation temperatures will be similar to those discussed above with respect to a degumming operation, 1. e., between approximate- 1;] 30 and 60 F. As discussed with respect to degumming operations, the desired temperature may be obtained by evaporation of solvent under controlled conditions and if a cooled oil from a degummlng operation-is being alkali-refined, any desiredaoljustments of temperature foreither the mixing or separation step may be accomplished by heating or cooling the oil, for example by indirect heat exchange, or in some cases the oil may be further cooled by evaporation of additional solvent.

If highly colored oils, such as solvent extracted cottonseed oil, are being alkali-refined, itis found that temperatures below approximately 60 F. promote the separation of coloring matter with the soapstock. The maximum color removal occurs in the neighborhood of 40 to 50 F., and While lower temperatures down to approximately 30 F. may be employed, there may be a slight increase in color below approximately 45 F. At the lower temperatures, 1. e., below 45 F., the timeof contact between the oil and refining agent for most effective color removal is usually greater than at higher temperatures. The minimum contact time between mixing and separation for most effective color removal depends somewhat upon the effectiveness of the mixing operation as well as upon the temperature. No definite minimum contact time, applicable to all conditions, can be Stated. The contact time can be increased over the required minimum time without damage to the oil since the caustic alkali does not appreciably attack the oil at the low temperatures contemplated. The requisite minimum contact time for effective color removal in any particular case is easily determined by the refiner. That to say, the amount of coloring matter which can be removed from the oil in a particular refining operation is adsorbed from the oil by the precipitated particles of soapstock in a short period of time and when this'occurs, separation can be immediately carried out as further time of contact does not appreciably lower the color of the oil.

As in the degumming operation, 'a large'portion of the unsaponifiables remain in the oil solvent mixture separated from soapstock. In the presence of the solvent and at the low temperature, the oil separates cleanly from the soapstock and there is substantially no attack of the alkali upon the glycerides. These factors,in conjunction with the fact'that a large proportion of the unsaponifiables remain in the oil, produces substantially increased recovery of neutral oil. The unsaponifiables which remain in the oil contain naturally occurring anti-oxidants which render the oil more stable against rancidity during any storage period between the alkali refining of the oil and further processing thereof.

In acid refining of solvent extracted oils to produce non-break oils, the maximum amount of solvent left in the oil should not exceed approximately of the oil. In general, the temperatures required for most effective acid refining in the presence of the solvent are substantially those discussed above with respect to the degumming and alkali-refining operations, the preferred range being between approximately and F. Again, this temperature may be obtained by evaporation of excess solvent. Acid refining procedures usually involve the addition of a small amount of concentrated sulfuric acid, for example 2% of 98% sulfuric acid. In acid refining operations as heretofore practiced, it is 'diificult to avoid charring and sulfation of the glycerides. At the low temperatures contemplated in the present invention, attack on the oil is minimized and the heat of reaction between the sulfuric acid and the impurities, such as mucilages, proteins and phosphatides, does not increase the temperature of the mixture to any significant extent. The oil solvent mixture separates cleanly from the coagulated mucilaginous material to produce an improved non-break oil. The acid refining of glyceride oils is ordinarily employed with linseed oils but may be applied to various other drying oils such as tung oil or semidrying oils such as soya bean oil intended for use in paints.

Any of the above refining steps may be carried out in a continuous manner and the preferred process contemplates the continuous mixing of a stream of oil-solvent mixture of the required proportions of oil and solvent and at the desired temperature with a stream of liquid refining agent after which the resulting stream is delivered to a continuous centrifugal separator. The desired time of contact between mixing and separation can be obtained in holding tanks through which the mixture may continuously flow and in which mild agitation is produced or by running the stream of mixture through pipe coils, such as shown in the Thurman patent, supra, or a combination of the two. The coils may be heatexchange devices for eifecting any desired adjustment of temperature between mixing and separa tion. While the oil-solvent mixture separates cleanly from the precipitated impurities at the low temperatures contemplated, the precipitated impurities such as soapstock from alkali refining or foots from the degumming or acid refining may in some cases be too viscous to flow readily from a continuous centrifugal separator. In such cases a heated centrifugal separator of the type disclosed in the patent to Clayton, No. 2,100,277, granted November 23, 1937, is advantageous and may be operated so as to heat only the heavier impurities being discharged and thereby reduce their viscosity and cause them to be readily discharged without substantially increasing the temperature at the zero of separation in the centrifugal. Alternatively, centrifugal separators of the type shown in the patent to Clayton, No. 2,301,109, granted November 3, 1942, may be employed with a carrier liquid to wash the separated heavier material from the centrifugal particularly if modified to deliver the carrier liquid to the extreme outer portion of the bowl or both heating of the separated impurities and a carrier liquid may be employed in the same centrifugal separator.

In general, the amount of solvent present in the oil being refined in any of the above operations.

7 including degumming, alkali refining or acid refining, will be approximately 25% although for alkali refining it may be as high as approximately 33%. Removal of the solvent down to 25% is relatively easily accomplished and in fact, no difficulty is encountered in removing the amount of solvent to between 5% and 10% of the oil by low temperature distillation. Removal of the remaining 5% to 10% of the solvent from crude oil does, however, present difiiculties. Either the temperature of distillation must be increased sufilciently to deleteriously affect the quality of the oil by modification of heat-sensitive impurities or a low temperature stream distillation step under high vacuum must be employed. In the latter case, difiicultly resolvable water and oil emulsions are produced due to the presence of the gums. The range of solvent content in the oil contemplated by the present invention where separate degumming and alkali refining steps are contemplated will, therefore, ordinarily be between 5% and 25% and the same range holds for acid refining. If alkali refining, even in the presence of gums, is to be carried out this range may be from approximately 5% to 33%. After the gums have been removed from the oil, either through a degumming operation, an acid refining operation or an alkali-refining operation, the remaining solvent is easily removed by vaporization thereof. In cases where a light colored oil is required from a highly colored oil, such as cottonseed oil, the removal of the excess coloring matter by alkali-refining in the presence of a proper amount of solvent also enables the remaining solvent to be easily removed at elevated temperatures without danger of setting the color in the oil.

The low temperature of separation contemplated makes winterizing of these oils, i. e., separation of saturated glycerides therefrom, relatively easy. By holding the oils in a quiscent state at temperatures between approximately 15 and 25 F., the stearine or other saturated glycerides will crystallize out of the oil and can be separated therefrom in any suitable manner, usually by filtration. The refined oil usually contains enough solvent to enable these temperatures to be easily secured by evaporation of at least a portion of such solvent under vacuum conditions although cooling by indirect heat exchange or addition of more solvent for evaporation can be carried out if necessary.

At still lower temperatures, for example between 20 and 15 F., fractionation of the oil in the presence of solvent can ordinarily be obtained. Thus, two fractions are produced, one containing solvent and the portion of the oil higher in unsaturated glycerides and the other portion, 1. e., the portion insoluble in the solvent, containing the portion higher in saturated glycerides. A separation between the two fractions can be readily obtained. This fractionation step is ordinarily applied to drying or semi-drying oils to obtain an unsaturated fraction having greater drying properties but may also be applied to edible oils to secure a more saturated fraction and thus a more stable oil. The step is of particular applicability to oils of semi-drying properties containing very little if any completely saturated glycerides, such as soya bean oil, to obtain an unsaturated fraction having increased drying Properties and a more saturated fraction 'particularly suitable for edible purposes. Either a step for separating saturated crystallized glycerides or a fractionating step may, however, be

employed with oil from a degumming step, an

:erably maintained relatively low, i. e., between 30 and 50 F.

Edible oils, particularly highly colored oils such as cottonseed oil, are ordinarily subjected to a bleaching operation after alkali refining. It is possible to perform a bleaching operation while the oil still contains from to 33% solvent. Such a bleachingoperation ordinarily involves the addition of a finely divided adsorbent, such as activated clay, carbon black, etc. This is followed by a filtering operation in which the adsorbent containing the adsorbed coloring material is filtered from the oil. By bleaching the oil while it still contains solvent, a final solvent removal step may be combined with a deodorizing step which usually involves steam distillation of the oil at high temperatures under a low vacuum. That is to say, the solvent may be vaporized from the oil in an initial portion of the deodorizing operation and condensed along with water. As the solvent is ordinarily immiscible with water, it may be easily separated from the water and returned to the solvent extraction operation. No separate solvent stripping step is required.

The process described above is applicable to oils extracted with any of the usual oil solvents employed in solvent extraction processes. The ordinarily used solvent is commercial hexane which is a mixture of hydrocarbons including hexanes and boils in the hexane range. For example, one commercial hexane is a water-white material having a specific gravity of 74.4 A. P. I. at 60 F., a boiling point range of 140-160 F., and a vapor pressure at 100 F. of 5.1 lbs. per square inch. Other oil solvents, for example, pure hexane, benzene, gasoline, petroleum ether, dichloroethylene, trichloroethylene, heptane, pentane, etc, may be employed. In general, solvents having a relatively low boiling point or high vapor pressure are preferred as the low temperatures contemplated in the present invention are more readily obtained with such solvents. Propane or similar solvents which are normally gaseous but which may be liquefied under pressure are "particularly useful. By carrying out the process under pressure the desired amount of solvent may be retained in the various mixtures and the required low temperatures may be secured by lowering the pressure on the system. In any event, it is preferred to carry out the process in a system which is substantially closed from the atmosphere to prevent loss of solvent.

As an example of the results obtained in an alkali refining operation even over the results of my prior copending app ication, supra, a highly colored cottonseed oil was selected and alkali refined at 70 F. The micella contained 33% petroleum ether during refining. A refined oil was produced having a color of 35 Y-9.0 R; the bleached oil had a color oi 30 Y2.8 R and the deodorized oil had a color of Y1.5 B. When another sample of the same micella was refined at a temperature of 48 F. the refined oil had a'color'o'f 35 Y' -5.3 R; the bleached oil had a color of 15 Y-l.5 R and the de'odorized oil had a color of '7 Y0.7 R. Another sample of the same micella was also refined at 32 F. in which case the color was very slightly higher than that of the oil refined at 48 P. All of the colors reported were determined by employing a Lovibond Tintometer using a 5%; inch column. All of these samples were refined under the same conditions except for different temperatures and in each case a 20 B. solution of caustic soda was employed in an amount providing for an excess of 0.5% of sodium hydroxide. The oil originally contained 0.9% free fatty acids and in all cases the separated oil was a neutral oil. The oil refined at 70 F. did not meet the standards of the industry as to color while the micella refined at 18 F. and 32 F. both were well within the standard with respect to color.

In all of the refining operations of the present invention including degumming, alkali refining and acid refining, the gum content in the separated oil, as shown by the phosphorous content, is lower than oils refined at higher temperatures. Also, a greater yield of higher quality oil is obtained.

While I have disclosed the prefered embodiments of my invention, it is understood that the details thereof may be varied within the scope of the fol owing claims.

I claim:

1. The process of refining a crude glyceride oil, which comprises, mixing an aqueous refining agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately 5% and 25% of volati e organic solvent for said oil ba ed on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said refining agent, said separating being performed at a temperature in said range, and thereafter vaporizing said solvent from said oil.

2. The process of partially refining crude glyceride oil, which comprises, mixing an aqueous degumming agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said degumming agent, said separating being performed at a temperature in said range, and thereafter vaporizing said solvent from said oil.

3. The process of alkali refining a crude glyceride oil, which comprises, mixing an aqueous alkali refining agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately 5% and 33% of volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture soapstock precipitated therein by said agent, said separating being performed at a temperature in said range, and thereafter vaporizing said solvent from said oil. 4

The process of acid refining a crude glyceride oil, which comprises, mixing an aqueous acid refining agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil While said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately and 25% of volatile organic solvent for said oil based on the Weight of said oil, continuously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said agent, said separating being per- Lformed at a temperature in said range, and thereafter vaporizing said solvent from said oil.

5. The process of refining a crude cottonseed oil, which comprises, mixing aqueous caustic alkali refining agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately 5% and 33% volatile organic solvent for said oil based on the weight of said oil, continuously centrifugally separating from the oil and solvent mixture soapstock including coloring matter precipitated therein by said agent, said separating being performed at a temperature in said range, and thereafter vaporizing said solvent from said oil.

6. The process of refining a crude glyceride oil, which comprises mixing aqueous degumming agent with said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said oil is at a temperature in the range of approximately 30 and 60 F. and is in admixture with between approximately 5% and 25% volatile organic solvent for said oil based on the weight of said oil, continu ously centrifugally separating from the oil and solvent mixture impurities precipitated therein by said degumming agent, said separating being performed at a temperature in said range, thereafter adding an alkali refining agent to the resulting oil and solvent mixture to precipitate additional impurities in said oil without substantial attack upon the glycerides of said oil While said resulting oil and solvent mixture is at a temperature in said range, continuously centrifugally separating from said resulting oil and solvent mixture soapstock precipitated therein by said alkali refining agent, the last-mentioned separating being performed at a temperature in said range, and thereafter vaporizing said solvent from said oil.

'7. The method of refining a solvent extracted crude glyceride oil containing a volatile organic solvent for said oil, which comprises, vaporizing a portion of said solvent from the micella resulting from a solvent extraction step to reduce the solvent content of the oil below approximately 25% but not less than approximately 5% based on the Weight of the oil, controlling the operating conditions during said vaporizing to bring the temperature of the resulting oil solvent mixture to a temperature in the range of approximately 30 to 50 F., mixing an aqueous refining agent with the resulting oil and solvent mixture to precipitate impurities in said oil without substantial attack on the glycerides of said oil, continuously centrifugally separating from the resulting oil and solvent mixture impurities precipitated therein by said refining agent, said mixing and separating each being performed at a temperature in said range, adding a finely divided ad sorbent to the resulting oil and solvent mixture to bleach said oil, separating said adsorbent i qm said resulting oil and solvent mixture, and thereafter subjecting said resulting oil and solvent mixture to steam deodorization under vacuum conditions to remove said solvent from said oil and deodorize said oil.

8. The method of refining a solvent extracted crude glyceride oil containing a volatile organic solvent for said oil, which comprises, vaporizing a portion of said solvent from the micella resulting from a solvent extraction step to reduce the solvent content of the oil below approximately 33% but not less than approximately 5% based on the weight of the oil, controlling the operating conditions during said vaporizing to bring the temperature of the resulting oil solvent mixture to a temperature in the range of approxi mately 30 to 50 F., mixing an aqueous refining agent with the resulting oil and solvent mixture to precipitate impurities in said oil without substantial attack on the glycerides of said oil, continuously centrifugally separating from the resulting oil and solvent mixture soapstock precipitated therein by said refining agent, said mixing and separating each being performed at a temperature in said range, adding a finely divided adsorbent to the resulting oil and solvent mixture to bleach said oil, separating said adsorbent from said resulting oil and solvent mixture, and thereafter subjecting said resulting oil and solvent mixture to steam deodorization under vacuum conditions to remove said solvent from said oil and deodorize said oil.

9. The process of refining a crude glyceride oil, which comprises, mixing a stream of liquid refining agent with a stream of oil-solvent mix ture containing between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil Without substantial attack upon the glycerides of said oil while said stream of oilsolvent mixture is at a temperature in the range of approximately 30 to 60 F., subjecting the resulting stream to continuous centrifugal separation while at a temperature in said range, to continuously separate from said oil and solvent, impurities precipitated in said oil and solvent mix-' ture by said refining agent and thereafter vaporizing the remaining solvent from said oil.

10. The process of refining a crude glyceride oil, which comprises, mixing a stream of aqueous degumming agent with a stream of oil-solvent mixture containing between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said stream of oil-solvent mixture is at a temperature in the range of approximately 30 to 60 F., subjecting the resulting stream to a continuous centrifugal separation while at a temperature in said range to continuously separate from said oil and sol vent mixture impurities precipitated in said oil and solvent mixture by said degumming agent and thereafter vaporizing the remaining solvent from said oil.

11. The process of refining a crude glyceride oil, which comprises, mixing a stream of aqueous alkali refining agent with a stream of oil-solvent mixture containing between approximately 5% and 33% of volatile organic solvent for said oil based on the Weight of said oil to precipitate i1npurities in said oil Without substantial attack upon the glycerides of said oil while said stream of oil-solvent mixture is at a temperature in the range of approximately 30 QQ 60 F., subjecting the resulting stream to continuous centrifugal separation while at a temperature in said range, to continuously separate from said oil and solvent mixture soapstock precipitated in said oil and solvent mixture by said refining agent and thereafter vaporizing the remaining solvent from said oil.

12. The process of refining a crude glyceride oil, which comprises, mixing a stream of concentrated mineral acid with a stream of oil-solvent mixture containing between approximately 5% and 25% of volatile organic solvent for said oil based on the weight of said oil to precipitate impurities in said oil without substantial attack upon the glycerides of said oil while said stream of oil solvent mixture is at a temperature in the range of approximately 30 to 60 F., subjecting the resulting stream to a continuous centrifugal separation while at a temperature in said range to continuously separate from said oil and 501- 20 vent mixture impurities precipitated in said oil and solvent mixture by said acid and thereafter vaporizing the remaining solvent from said oil. MORRIS MATTIKOW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,408,804 Gleitz Mar. 7, 1922 2,260,731 Thurman Oct. 28, 1941 2,288,441 Ewing June 30, 1942 2,380,412 Buxton July 31, 1945 FOREIGN PATENTS Number Country Date 308,250 Great Britain Mar. 6, 1930 2,380,413 Buxton July 31, 1945 

1. THE PROCESS OF REFINING A CRUDE GLYCERIDE OIL, WHICH COMPRISES, MIXING AN AQUEOUS REFINING AGENT WITH SAID OIL TO PRECIPITATE IMPURITIES IN SAID OIL WITHOUT SUBSTANTIAL ATTACK UPON THE GLYCERIDES OF SAID OIL WHILE SAID OIL IS AT A TEMPERATURE IN THE RANGE OF APPROXIMATELY 30* AND 60* F. AND IS IN ADMIXTURE WITH BETWEEN APPROXIMATELY 5% AND 25% OF VOLATILE ORGANIC SOLVENT FOR SAID OIL BASED ON THE WEIGHT OF SAID OIL, CONTINUOUSLY CENTRIFUGALLY SEPARATING FROM THE OIL AND SOLVENT MIXTURE IMPURITIES PRECIPITATED THEREIN BY SAID REFINING AGENT, SAID SEPARATING BEING PERFORMED AT A TEMPERATURE IN SAID RANGE, AND THEREAFTER VAPORIZING SAID SOLVENT FROM SAID OIL. 